In recent years, the organic electroluminescent device having high efficiency and fluorescent dyes, can be used for the flat panel displays to bring this technology commercialization. In various types of flat panel displays, since an OLED, being developed later than a liquid crystal display (LCD), has many beneficial characteristics, such as a spontaneous light source, a wide viewing angle, high response velocity, high brightness, strong contrast, small thickness, power saving, and a wide operating temperature, the OLED has been used extensively in small and medium scale portable display fields.
The emitting layer is between the metal cathode and transparent anode in the organic electroluminescent device. When a DC voltage is applied to the OLED structure, electrons in the cathode and holes in the transparent conductive layer will be injected into the emitting layer through the electron transport layer and the hole transport layer respectively. Due to the potential difference incurred from the external electrical field, electrons and holes will move in the emitting layer and recombine as excitions. When the excitions come back to the ground state by way of releasing energy, the quantum efficiency is released in a form of photons to emit light downwards through the transparent anode. This is the organic electroluminescent principle.
For example, in U.S. Pat. No. 6,465,115 disclosed anthracene compound on the hole transport layer, which on position 9 and 10 having aryl group, the structure as following:
wherein substituents R1 to R4 are each individually hydrogen, or alkyl of from 1 to 24 carbon atoms; aryl or substituted aryl of from 5 to 20 carbon atoms; or heteroaryl or substituted of from 5 to 24 carbon atoms; or fluorine, chlorine, bromine; or cyano group.
In U.S. Pat. No. 5,759,444 also disclosed anthracene compound, the structure as following:
wherein each of A1 to A4 are a substituted or unsubstituted aryl group having 6 to 16 carbon atoms, and each of R1 to R8 are a hydrogen atom independently, a halogen atom, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted aryl groups or a substituted or unsubstituted amino group.
In U.S. Pat. No. 6,310,231 disclosed silane compounds as a constituent material of luminescent device are described, which are represented by following formula:
wherein R1 represents an alkyl group, an aryl group, a heteroaryl group or an alkynyl group, and each of Ar11, Ar12, and Ar13 represent a heteroaryl group.
Though the prior investigations described the organic light emitting diode, it is very important to make new and efficient organic EL materials to improve the spontaneous light source, a wide viewing angle, high response velocity, high brightness, strong contrast, small thickness, power saving, and a wide operating temperature in the organic electroluminescent device.